Ultrahigh energy storage density and efficiency in AgNbO₃-based ceramics by percolating interaction between antipolar regions and defect pairs

A critical challenge for the application of lead-free antiferroelectrics in energy storage systems is their poor thermal stability and low efficiency when the superior energy storage density is attained, primarily due to the inherent first-order nature and narrow temperature window of antiferroelectric-to-ferroelectric transitions. Here, we elucidate a unique percolating interaction between antipolar regions in antiferroelectrics and engineered defect pairs using density functional theory and phase field calculations. Strategic distribution of the strongly coupled Li-Ta pairs in AgNbO₃ fosters a percolating interaction that facilitates antipolar rotations, enabling a pronounced polarization change with minimal hysteresis. Guided by theoretical calculations, a large recoverable energy storage density of 12.8 J/cm³, with a high efficiency of 90%, is achieved at room temperature in Ag_0.95Li_0.05Nb_0.35Ta_0.65O₃ ceramics. Moreover, the superior energy storage performance can remain stable within a wide temperature range from −70 to 170 °C, which paves the way for application in advanced energy capacitors.